Brief intorduce of Steel structure engineering

Steel structure engineering is a structure mainly made of steel. It is mainly composed of steel beams, steel columns, steel trusses and other members made of sections and steel plates. Welding seams, bolts or rivets are usually used to connect each member or component, which is one of the main structural types of buildings. Due to its light weight and simple construction, it is widely used in large workshops, stadiums,super high-rise buildings and other fields.

Steel structure features

The dead weight of steel structure is light

The reliability of steel structure is high

The good seismic performance and impact resistance

The steel structure can be assembled accurately and quickly

The industrialization is high of steel structure manufacturing

The interior space is large of steel structure

Easy to make seal structure

The progress of development

Although China make brilliant accomplishment in steel structure in the early age, it remains the level of iron building due to the two thousand years of constraint of feudal system.Until the end of the 19th,China started to adopt to modern steel structure. After the founding of new china,the application of steel structure has developed greatly, both quantity and quality are far more than the past. Not only achieved the great achievement in technical aspect of designing,manufacturing,and installation but also master all kinds of design and construction technique of complicated building. Besides, many large scale and complex structure steel structure workshop,large span steel structure civil building and railway bridge have been built all over the country, such as steel roof truss frame of Great hall of the people in China, the steel frames for stadiums of Beijing and Shanghai, the three-hinged steel arch of the Exhibition Hall of Qin Shihuang's Soldiers and Horses and steel structure project of bird’s of Beijing

Superiority of steel structure building

1.Seismic performance: 

The roof of the low-rise villas are mostly sloped roofs, so the roof structure is basically a triangular roof truss system made of cold-formed steel members. The light steel members form a very strong after the structural plate and gypsum board are sealed "Slab rib structure system", this structure system has a stronger ability to resist earthquakes and resist horizontal loads, and is suitable for areas where the seismic intensity is above 8 degrees.

2.Wind resistance: 

The steel structure building has light weight, high strength, good overall rigidity and strong anti-deformation ability. The weight of the building is only one-fifth of the brick-concrete structure, which can resist a hurricane of 70 meters per second, so that life and property can be effectively protected.

3.Durability: 

The light steel structure residential structure is all made of cold-formed thin-walled steel component system. The steel skeleton is made of super anti-corrosion high-strength cold-rolled galvanized sheet, which effectively avoids the corrosion of the steel plate during construction and use and prolong the life span of the light steel component. The structural life can reach 100 years.

4.Heat preservation:

The thermal insulation material used is mainly glass fiber cotton, which has good thermal insulation effect. The insulation board of the outer wall is used to effectively avoid the phenomenon of "cold bridge" of the wall and achieve a better insulation effect. The thermal resistance value of the R15 insulation cotton with a thickness of about 100mm can be equivalent to a brick wall with a thickness of 1m.

5.Acoustical insulation: 

The sound insulation effect is an important indicator to evaluate the residence. The windows installed in the light steel system all use hollow glass, which has good sound insulation effect, and the sound insulation effect is more than 40 dB. The sound insulation effect of the wall composed of light steel keel and insulation material gypsum board can be as high as 60 dB.

6.Health:

Dry construction, reduce the pollution caused by waste to the environment, housing steel structure materials can be 100% recycled, other supporting materials can also be mostly recycled, in line with current environmental awareness; all materials are green building materials, meet the ecological environment requirements, good for health.

7.Comfort:

The light steel wall adopts an efficient energy-saving system,which has a breathing function and can adjust the indoor air dry humidity; the roof has a ventilation function, which can form a flowing air space above the house to ensure the ventilation and heat dissipation requirements inside the roof.

8.Quickness: 

All dry work construction is not affected by environmental seasons. In a building of about 300 square meters, only 5 workers and 30 working days can complete the whole process from foundation to decoration

9.Energy saving and Environmental protection: 

All adopt high-efficiency energy-saving walls, with good thermal insulation, heat insulation and sound insulation effects, and can reach 50% energy saving standard. The material can be recycled 100%, truly green and pollution-free.

The key to the production of steel structure workshop and steel structure warehouse is design. Only rigorous and reasonable design can guide construction personnel to make economical and practical workshop/warehouse.

According to the summary of professional, the following five points must be noted in the design of the workshop/warehouse:

1. Insulation and fireproof of steel materials:

Steel materials has high thermal conductivity, and its thermal conductivity is 50w (m.℃). When heated to more than 100℃, its tensile strength will decrease and plasticity will increase. When the temperature reaches 250℃, the tensile strength of the steel will increase slightly, but the plasticity will decrease, and the phenomenon of blue brittleness will appear; When the temperature reaches 500 ℃, the strength of the steel drops to a low level, which will cause the steel structure to collapse. Therefore, when the ambient temperature of the steel structure reaches more than 150 ℃, heat insulation and fireproof design must be done.

2. Roof support system and roof design:

The layout of the roof support system is determined by the span, height, column grid layout, roof structure, crane tonnage, and seismic fortification intensity of the area. In general, the roof structure with purlin or no purlin system should be provided with vertical supports; In a system without purlins, the large roof panel has three points welded to the roof truss, which can play a supporting role in the winding. However, considering the limitation of construction condition and installation requirement, both purlin and without purlin system should be provided with upper string transverse support of roof truss and skylight.
Longitudinal horizontal support shall be provided for the factory buildings with a roof frame spacing of not less than 12m or those with heavy bridge cranes or large vibration equipment in the factory buildings.

3. Setting of temperature expansion joint:

The change of temperature will cause the deformation of steel structure workshop, which will cause the temperature stress of the structure. When the plane scale of the workshop is large, in order to avoid greater temperature stress, temperature expansion joints should be set in both vertical and horizontal directions of the workshop. The length of the section can be implemented according to the steel structure specification. Temperature expansion joints are generally handled by the method of setting double columns. For longitudinal temperature expansion joints, rolling supports can be provided at the roof support.

4. Anti-rust treatment:

The surface of the steel structure will corrode if directly exposed to the air. When there is corrosive medium in the air or the steel structure is in a humid environment, the corrosion of the steel structure workshop will be more serious. The corrosion of the steel structure will not only reduce the cross section of the component, but also cause local rust pits on the surface of the steel component. Stress concentration phenomenon is caused when the component is under force, which leads to premature failure of the structure. Therefore, we should pay more attention to the problem of anti-corrosion of steel structure workshop components.

5. Facade design:

The construction of light steel structure mainly grasps the characteristics of the following four aspects: scale, line, color and change. The facade of the steel structure workshop is mainly determined by the process layout. In order to meet the requirements of craftsmanship, strive to make the facade simple and magnificent, and at the same time make the nodes as simple and unified as possible. The color profiled steel plate makes the construction of the light steel factory building appear light and colorful, which is obviously superior to the traditional heavy reinforced concrete structure. In the design of light steel workshop, jumping colors and cool colors are often used, with emphasis on the main entrances and exits, outer gutters, and edge flooding, which not only embodies the magnificence of modern factories, but also enriches the facade effect.

Steel structure is one of the common structural forms in modern architectural engineering.Steel structure installation technology is more and more widely used in our country, and many advantages of steel structure are valued, and the application of steel structure is also increased. This paper analyzes the installation technical requirements of the steel structure project to strengthen the technical application and management of the steel structure project and ensure the safety and reliability of  the entire  steel structure project.

Single-layer portal frame installation

The single-span structure should be hoisted in order from one side of the span end to the other side, middle to both ends, or both ends to the middle. For multi-span structure, it is advisable to hoist the main span first and the sub-span afterwards; when multiple cranes work together, they can also be hoisted at the same time. The single-layer portal frame steel structure should be installed in the order of upright column, connecting beam, column bracing, crane beam, roof frame, purline, roof bracing and roof panel.

During the installation of the portal frame structure, the temporary column bracing  or the cable wind rope needs to be installed in time, and it can be expanded and installed after forming a stable space structure system.The stable space structure system should be able to withstand the effects of structural dead weight, wind load, snow load, earthquake action, installation load and impact load during hoisting.

Multi-layer and high-rise steel structure project installation

1.The installation of multi-story and high-rise steel structures should be divided into multiple flow operation sections for installation. The division of flow section should meet the following requirements:

1).The heaviest member in the flow section should be within the hoisting capacity of the hoisting machine;

2).The climbing height of lifting equipment should meet the lifting height of the members in the lower throttle water section

3).The length of the column in each section of water should be determined according to factors such as factory processing, transportation and stacking, site hoisting, etc. The length should be 2 to 3 floors high, and the section location should be 1.0 to 1.3m above the beam level

4).The division of the steel structure flow section should be compatible with the installation of the concrete structure;

5).According to the structural characteristics and site conditions, each flow section can be divided into planes for installation

2.The hoisting of components in the assembly line section should meet following requirements:

1).The hoisting can adopt the order of the first column and the second beam in the whole flow section, or the order of the first column and the second beam; the single column cannot be in the cantilever state for a long time;

2).The installation of steel floor and pressed metal plates should be synchronized with the progress of component lifting;

3).The hoisting sequence in the special flow section should be determined according to the installation process and should meet the requirements of the design documents.

3.The installation and calibration of multi-layer and high-rise steel structures should be based on the reference column and should meet the following requirements:

1).The reference column should be able to control the plane size of the building and facilitate the correction of other columns. The corner column should be selected as the reference column

2).Appropriate measuring instruments and calibration tools should be used for steel column calibration

3).After the calibration of the reference column is completed, other columns shall be calibrated

4. During the installation of multi-layer and high-story steel structures, the floor elevation can be controlled by relative elevation or design elevation, and should meet the following requirements: 

1).When design elevation control is adopted, the column elevation should be adjusted in units of each column, and the elevation of each column should be meet the design requirements;

2).The allowable deviation of the total height of the building and the difference in height of the column tops of the columns in the same floor shall comply with the relevant provisions of the current national standard "Code for the Acceptance of Installation Quality of Steel Structure Engineering" GB50205.

3).For the same pipeline operation section and the same installation height, when all the components of each column are installed, calibrated, connected, and accepted, the positioning axis of the previous section should be placed from the ground. During the installation of high-rise steel structures, the impact of vertical compression deformation on the structure should be analyzed, and corresponding measures such as pre-adjusted installation elevation and connecting members after installation should be taken according to the structural characteristics and the degree of influence.